Download Proteins

Proteins
Proteins:
Multipurpose molecules
Proteins
Examples
– muscle
insulin
– skin, hair, fingernails, claws
• collagen, keratin
pepsin
– pepsin
• digestive enzyme
in stomach
– insulin
• hormone that controls blood sugar
levels
collagen (skin)
• Function:
Proteins
– many, many functions
• hormones
– signals from one body system to another
– insulin
• movement
– muscle
• immune system
– protect against germs
• enzymes
– help chemical reactions
Proteins
• Building block =
amino acids
amino amino amino amino amino
acid – acid – acid – acid – acid

20 different amino acids
H O carboxyl
H
| ||
—N—
—C—C—OH
|
H
Alpha carbon
Amino
group
variable
group
There’s
20 of us…
like 20 different
letters in an
alphabet!
Can make lots of
different
words
Amino acid chains
• Proteins
– amino acids chained into a polymer
amino acid
amino acid
amino acid
amino acid
amino acid
• Each amino acid is different
– some “like” water & dissolve in it
Polypeptide
– some “fear” water & separate from it bond
Water-fearing amino acids
• Hydrophobic
– “water fearing” amino acids
– try to get away from water in cell
• the protein folds
Water-loving amino acids
• Hydrophillic
– “water loving” amino acids
– try to stay in water in cell
• the protein folds
For proteins: SHAPE matters!
• Proteins fold & twist into 3-D shape
– that’s what happens in the cell!
• Different shapes = different jobs
growth
hormone
hemoglobin
pepsin
collagen
It’s SHAPE that matters!
• Proteins do their jobs, because
of their shape
• Unfolding a protein destroys its shape
– wrong shape = can’t do its job
– unfolding proteins = “denature”
• temperature
• pH (acidity)
In Biology,
it’s not the size,
it’s the SHAPE
that matters!
folded
unfolded
“denatured”